Adaptability of mastication in people with implant-supported bridges.

OBJECTIVES: We aimed to determine whether people with implant-supported bridges in both jaws, thus lacking periodontal receptors, adjust jaw muscle activity to food hardness during mastication.
MATERIALS AND METHODS: Thirteen participants with implant-supported bridges in both jaws and 13 with natural dentition chewed and swallowed soft and hard gelatine-based model foods, while electromyographic (EMG) activity of the masseter and temporal muscles was recorded bilaterally together with the position of the mandible. Data were compared by using a mixed-design anova model and a P-value<0.05 was considered statistically significant.
RESULTS: The number of chewing cycles and the duration of the masticatory sequence increased with food hardness in both groups, whereas vertical and lateral amplitude of the jaw movements, and the jaw-opening velocity, increased significantly with food hardness only for the dentate group. Although both groups adapted the EMG activity to the hardness of the food, the implant participants showed a significantly weaker increase in EMG activity with increased food hardness early during the masticatory sequence than the dentate participants did. In addition, the implant group showed significantly less reduction of muscle activity during the progression of the masticatory sequence than the dentate group.
CONCLUSIONS: People with implant-supported bridges show an impaired adaptation of the muscle activity to food hardness during mastication. We suggest that a lack of sensory signals from periodontal mechanoreceptors accounts for the impairment.